git add

tests/fs/special.rs

@@ -0,0 +1,57 @@
+#[cfg(not(target_os = "wasi"))]
+#[test]
+fn test_special_fds() {
+    use rustix::fs::{fstat, open, openat, Mode, OFlags, Stat, ABS, CWD};
+    use rustix::process::getcwd;
+    use std::ffi::OsStr;
+    use std::os::unix::ffi::OsStrExt;
+    use std::path::PathBuf;
+
+    let cwd_path = getcwd(Vec::new()).unwrap().into_bytes();
+    let cwd_path = OsStr::from_bytes(&cwd_path).to_owned();
+    let cwd_path = PathBuf::from(cwd_path);
+
+    // Open the same file several ways using special constants and make sure
+    // we get the same file.
+
+    // Use plain `open`.
+    let a = open("Cargo.toml", OFlags::RDONLY, Mode::empty()).unwrap();
+
+    // Use `CWD` with a relative path.
+    let b = openat(CWD, "Cargo.toml", OFlags::RDONLY, Mode::empty()).unwrap();
+
+    // Use `CWD` with an absolute path.
+    let c = openat(
+        CWD,
+        cwd_path.join("Cargo.toml"),
+        OFlags::RDONLY,
+        Mode::empty(),
+    )
+    .unwrap();
+
+    // Use `ABS` with an absolute path.
+    let d = openat(
+        ABS,
+        cwd_path.join("Cargo.toml"),
+        OFlags::RDONLY,
+        Mode::empty(),
+    )
+    .unwrap();
+
+    // Test that opening a relative path with `ABS` fails.
+    let err = openat(ABS, "Cargo.toml", OFlags::RDONLY, Mode::empty()).unwrap_err();
+    assert_eq!(err, rustix::io::Errno::BADF);
+
+    let a_stat = fstat(a).unwrap();
+    let b_stat = fstat(b).unwrap();
+    let c_stat = fstat(c).unwrap();
+    let d_stat = fstat(d).unwrap();
+
+    assert!(same(&a_stat, &b_stat));
+    assert!(same(&b_stat, &c_stat));
+    assert!(same(&c_stat, &d_stat));
+
+    fn same(a: &Stat, b: &Stat) -> bool {
+        a.st_ino == b.st_ino && a.st_dev == b.st_dev
+    }
+}